Fallout lore hasn't expanded to cover much about countries other than the United States, China included.
It was very clearly nuked in reprisal, although no one knows how badly. In Fallout 2 President Richardson says it was basically turned to radioactive glass by the American counterstrike, but he's not entirely trustworthy, and that would be an odd thing to do, considering that part of it occupied by US conventional forces at the time. Otherwise no one knows - not even the Shi have had any subsequent contact, and Moira Brown thinks it's probably fictional.
I don't know, but when a topic like this comes up, it makes me think; the next Fallout game needs to be placed in China.